Book Reviews - A rumble in the jungle. A journalistic expose, which is unlikely to be published here because of our restrictive libel laws, has caused a sensation in the US with its allegations of genocide in the Amazon and academic subterfuge. Kenan Malik reads a devastating attack on anthropology

There have been few scientific disciplines with a history as sordid, fractious and ideologically riven as anthropology. The academic study of the "other" has more often than not reflected political and social aims, and the methods of anthropology have swung violently, sometimes virtually overnight, as those political and social aims have changed. In the 19th century, anthropology developed as the handmaiden of imperialism, providing in racial science a justification of European superiority and barbarism. "What signify these dark races to us?" asked the biologist Robert Knox in 1850. "Destined by the nature of their race to run, like all other animals, a certain limited course of existence, it matters little how their extinction is brought about."

The consequences of racial science led 20th-century anthropologists to reject naturalistic explanations and to believe human behaviour to be dictated largely by culture, not biology. The desire to undermine racism led, however, to a new set of myths about human behaviour: all too often, anthropologists saw what they wanted to. A classic case in point was Margaret Mead, whose Coming of Age in Samoa became one of the most famous anthropological works. Mead described an idyllic society, unconstrained by the sexual neuroses that characterised American society. Her message was simple: human sexual mores are shaped by culture, and it is modern civilisation that made us neurotic about sex.

In the 1980s, however, the Australian anthropologist Derek Freeman revealed that much of Mead's data was fraudulent: she had seen only what she wanted, and native Samoans had co-operated, telling her what she wanted to hear. Freeman's destruction of Mead's work was eagerly seized on by a new generation of an- thropologists who, inspired by sociobiology, sought to rehabilitate evolutionary explanations of behaviour.

The most prominent of the new generation of sociobiological anthropologists was the American Napoleon Chagnon. In 1964, as a young student, he travelled deep into the Amazon rainforest, to the wild borderlands of Brazil and Venezuela, to begin a lifetime of study of an almost unknown group of people called the Yano-mami. Nearly four decades of fieldwork transformed the Yanomami into just about the most famous tribal group in the world - and Chagnon into the most celebrated anthropologist. His book Yanomamo: the fierce people (1968) quickly became one of the most popular anthropological works of all time, selling more than a million copies.

Chagnon presented the Yano-mami as a fierce, primitive tribe whose mores opened the window on to our own past ("our contemporary ancestors", he called them). Most controversially, he linked Yanomami violence to genetic success. In a paper published in the prestigious journal Science in 1988, Chagnon reported that 30 per cent of all Yanomami males from his study group were killed in warfare, while 44 per cent had murdered someone. Most dramatically, he revealed that the killers had more than twice as many wives and three times as many offspring as non-killers. The idea that murderous violence enhanced Yanomami men's reproductive success was manna for sociobiologists.

Chagnon's paper is one of the most widely cited scientific studies of all time - and one of the most fiercely criticised, too. An academic war erupted in the early 1990s as other Amazonian specialists questioned Chagnon's data, methods and statistics. They also questioned his politics. The anthropologist Leslie Sponsel, for instance, opposed the "Darwinian emphasis on violence and competition", promoting instead an "anthropology of peace". He remained convinced that "non-violence and peace were likely the norm throughout most of human prehistory" and that "intrahuman killing was probably rare".

Many of Chagnon's supporters, on the other hand, embraced his work precisely because it questioned such assumptions, suggesting instead that humans are inherently violent and aggressive. Chagnon himself has said that violence "may be the principal driving force behind the evolution of culture", and that his work debunks "all that crap about the Noble Savage".

Into this debate now comes the US journalist Patrick Tierney's Darkness in El Dorado, an incendiary device lobbed into a crowded room if ever there was one. Tierney spent a decade investigating the impact of anthropologists (and, in particular, Chagnon) on the Yanomami. Many have compared his dissection of Chagnon's work to Freeman's expose of Mead. But Freeman charged Mead only with being naive and carried away by her political enthusiasm. Tierney accuses Chagnon, among other things, of scientific fraud, sexual abuse, political corruption and, most sensationally, genocide. According to Tierney, Chagnon and his mentor, the geneticist James Neel, may have deliberately infected Yanomami with measles, beginning an epidemic that wiped out hundreds, perhaps even thousands, as part of a grotesque experiment testing the impact of natural selection on primitive groups. Even those familiar with the depressing history of anthropology have been shocked by Darkness in El Dorado.

Not surprisingly, the book (which is unlikely to be published in Britain because of our restrictive libel laws) has caused a huge commotion in America, both inside and outside the academy. The anthropologists Terence Turner and Leslie Sponsel have written of Chagnon's work that in its "scale, ramifications and sheer criminality and corruption it is unparalleled in the history of anthropology". Tierney's book, they claim, is "a case study of the dangers in science of the uncontrolled ego".

The debate presents neither side in a flattering light. Socio- biologists have dismissed all criticism of Chagnon as politically motivated, ignoring genuine problems with his work. Blinded by their dislike of sociobiology, many of Chagnon's critics have been all too willing to ride roughshod over the facts in turning a critique of Chagnon into a moral crusade.

Tierney's critics have, in turn, described his book as a "hoax", and the campaign against Chagnon as a witch-hunt led by Marxists and postmodernists. Many of the biggest names in academia - including E O Wilson, Richard Dawkins and Steven Pinker - have rallied to Chagnon's side, as has the National Academy of Sciences. The conservative National Review claimed that "Chagnon is the target of one of the greatest smear campaigns ever waged against a scholar".

The most important part of Tierney's critique is the least original (and the least sensational) - his dissection of Chagnon's methodology. Drawing on the work of another Yanomami scholar, Brian Ferguson, Tierney presents a convincing case that Chagnon has consistently overestimated Yanomami violence, and that he himself was responsible for fomenting much of it. In Yanomami Warfare: a political history, Ferguson revealed how Chagnon had changed the political balance between different Yanomami groups by favouring some over others, and by selectively providing steel goods and weapons to certain groups. Chagnon often burst into villages decorated in warpaint and brandishing a shotgun.

Yanomami men soon realised that their own displays of aggression would win them machetes and other highly prized tools. According to Ferguson: "A war started between groups which had been at peace for some time on the very first day Chagnon got there, and it continued until he left." Far from being an objective observer of Yanomami violence, Chagnon was an active participant in the wars. Yanomami men were fighting for access not to women, but to Chagnon himself.

Tierney's figures show that the violence of a Yanomami group depended largely on where its particular village was sited. Highland villages, distant from contact with outsiders, tended to be more peaceable. Lowland villages, especially those sited along rivers, had greater contact with outsiders - including missionaries, the American army and anthropologists - and tended to be far more violent. Of the Yanomami group that Chagnon studied, violent deaths were not chronic, but peaked in two periods. One was between 1949 and 1951, when there was a US army expedition in the area. The other was be-tween 1964 and 1966, the dates of Chagnon's anthropological study. "The question is no longer why the Yanomami are so fierce," Tierney writes, "but why Chagnon's Yanomami have homicide rates so much higher than those of other Yanomami groups."

For most readers, however, the heart of Tierney's book will not be his critique of Chagnon's methodology, but his far more sensational claim that Chagnon participated in mass murder. The Yanomami, like many isolated populations, are vulnerable to diseases to which westerners have acquired immunity. Over the past five centuries, millions of indigenous people throughout the Americas have died of "old world" germs to which they had never before been exposed and, hence, had neither immune nor genetic resistance. One such disease is measles. In 1968, a measles epidemic laid waste to the Yanomami population. At exactly the same time, Chagnon had embarked on an expedition to the Amazon under the leadership of the geneticist James Neel. During that expedition, the two men initiated a programme of inoculation against measles to protect the Yanomami. According to Tierney, however, it was that very programme of inoculation that caused the epidemic in the first place.

Neel and Chagnon used a primitive form of measles vaccine, known as Edmonston B, which contained a live virus and was very virulent. In a population as vulnerable as the Yanomami, Tierney claims, it led inevitably to an epidemic. Tierney quotes several people who hint darkly that an epidemic might have been exactly what Neel wanted. Moreover, once the epidemic was under way, Neel and Chagnon "refused to provide any medical assistance to the sick and dying Yanomami", insisting that "they were there only to observe and record the epidemic, and that they must stick strictly to their roles as scientists, not provide medical help". This was, in Tierney's words, "science in the service of ethnocide".

But why would Neel and Chagnon wish to spread measles among the Yanomami? Because, Tierney suggests, Neel was a eugenicist, and the Yanomami inoculation programme was an exercise in covert eugenics. Neel chose to inoculate the Yanomami with Edmonston B "precisely because it was primitive, [and] provided a model much closer to real measles than other safer vaccines in the attempt to resolve the great genetic question of genetic adap-tation". Tierney suggests that Neel rejected the medical orthodoxy that the Yanomami were genetically susceptible to measles, believing that their survival-of-the-fittest lifestyle had given them immune systems more robust than those in more pampered modern societies. The epidemic would prove Neel's theories.

If Tierney's story is true, then it has devastating consequences for the reputation of both Neel (who died earlier this year) and Chagnon, proving them guilty of a murderously criminal act. It would also throw into doubt all of Chagnon's other work - including his theories about the link between violence and reproduction. The trouble is, however, that Tierney produces very little direct evidence to back up his monstrous claims. Darkness in El Dorado relies entirely on circumstantial evidence, hearsay and questionable interpretations of film of Neel and Chagnon at work.

There is little doubt that Neel was a eugenicist who believed that the problems of modern society arose "primarily from abandoning the population structure and the selective pressures under which humankind evolved". Humans originally evolved in small, relatively isolated tribal groups, in which men competed with one another for access to women. In such societies, Neel assumed, the best fighters would have the most wives and children, and pass on more of their genetic "index of innate ability" to the next generation. This was exactly the argument that Chagnon was later to make about the character of Yanomami society.

Neel's views may seem distasteful and reactionary. But they were common to scholars of his generation, who had been brought up in a prewar intellectual climate largely shaped by racial science. Acknowledging Neel's belief in eugenics is no reason to assume that he would act in the manner of Josef Mengele. Indeed, far from showing that Neel and Chagnon deliberately began the measles epidemic, the evidence suggests the very opposite. The consensus is that the measles epidemic began before Chagnon and Neel arrived in Venezuela, and that they initiated their inoculation programme precisely because they were aware of the earlier outbreak. They used Edmonston B not because of Neel's crackpot theories, but after receiving advice from the Venezuelan government.

In the wake of the furore about Tierney's book, the historian Susan Lindee has checked Neel's field notes for the 1968 expedition. Neel, she acknowledges, was "a Cold Warrior deluxe, confident in his hierarchical rankings of races, sexes, civilisations". But, she concludes, there is no evidence either that he began the epidemic or that he "attempted to discourage anyone from providing treatment", as Tierney claims. Indeed, Lindee writes: "for about two weeks [Neel] spent much of his own time administering vaccines and antibiotics."

In many ways, Darkness in El Dorado raises as many questions about Tierney's motives, and those of Chagnon's other critics, as it does about Chagnon's own work. It is one thing to accuse a scholar of having poor judgement, or of using misleading data. It is quite another to accuse him of mass murder. Before one even begins to think about making public such a charge, one requires considerably more than simply circumstantial evidence, supposition and insinuation based on a dislike of a scientist's methodology and politics. It is astonishing not only that Tierney should make such monstrous claims on such flimsy evidence, but also that so many leading anthropologists should support him in doing so.

However, for Tierney, as for many of his supporters, anthropology is less a scientific discipline than a political mission. The aim of anthropologists, in their view, is to defend the dispossessed. Tierney has been an active participant in the political struggles in the Amazon, seeking to defend Yanomami rights against claims made by gold-miners and the Brazilian government. To him, socio-biology is not so much a scientific method as a political programme. Chagnon's depiction of the Yanomami, he believes, has opened the way for the use of violence against them by miners and government officials. "As a result," Tierney writes, "I gradually changed from being an observer to being an advocate." And he says: "traditional, objective journalism was no longer an option for me."

What Tierney is questioning is the very possibility of a scientific anthropology. Anthropologists cannot simply be observers, as traditional scientific objectivity requires, but must actively take sides in any political struggle involving the peoples they are studying. And in such a struggle, the norms of scientific objectivity become subordinate to the political aims. It's an ironic argument given Tierney's own critique of Chagnon for his lack of objectivity and for becoming a participant in, rather than an observer of, Yanomami affairs.

I have long been critical of sociobiology and evolutionary psych-ology. I find its methods flawed, its arguments naive, its claims often veering from the banal to the bizarre. But there can be no critique of sociobiology if we dismiss the possibility of a scientific study of humankind. Darkness in El Dorado raises important questions about anthropological methodology in general and Chagnon's work in particular. But it unwittingly raises equally troubling questions about the methods and motives of Chagnon's critics.

Kenan Malik's Man, Beast and Zombie is published by Weidenfeld & Nicolson (£20)